Bristles with surface structure, method for their manufacture and interdental cleaner or brush manufactured therefrom

ABSTRACT

A method for the manufacture of surface-structured bristle material from plastic by extruding a monofilament. Before or during extrusion a granular material is admixed with a thermally melted first plastics material forming the main component of the monofilament. The granular material comprises a second plastics material, which has a higher thermal strength than the first plastics material. The particle size of the granular material is such that the monofilament, during a subsequent stretching, is subject to a greater transverse contraction in cross-sections where there is little or no granular material than in cross-sections containing granular material. A disclosed bristle included a surface structure from a first plastics material forming the main component of the bristle and in which is embedded in a substantially completely covered manner a granular material of a second plastics material, the granular material forming a structuring on the bristle surface. A brush, particularly a toothbrush or interdental cleaner, with a plurality of bristles, optionally combined into bundles and in which at least certain bristles have the aforementioned structure, is also disclosed.

TECHNICAL FIELD

The invention relates to bristles with a surface structure and to amethod for the manufacture of surface-structured bristle material fromplastic by extruding a monofilament. The invention also relates to abrush, particularly a toothbrush or interdental cleaner, which is atleast partly provided with the surface-structured bristles.

Although the invention is described hereinafter in conjunction withbristles and bristle material, it expressly covers monofilaments, whichcan be processed to fabrics, mats, filters, etc. The invention can alsobe used in the case of paint brushes, polishing and abrading pads orcleaning, application, polishing or abrading devices.

BACKGROUND OF THE INVENTION

Plastic bristles which are extruded are normally smoothed on theirsurface due to the manufacturing process. In the case of brushware of arandom nature, such bristles exercise their brushing action initiallyand mainly through the free ends of the bristles, which tear open thedirty surface and remove the dirt by scratching and scraping. In thecase of stronger pressure, the bristles are bent round and act withtheir circumferential surface. They then slide in a stroking and slidingmanner over the surface with a more gentle action. Also when applyingpaint and the like by means of a brush the bristles are curved or bent,so that they engage with the surface to be treated not only with theirfree bristle ends, but also with their circumferential surface. For along time consideration has been given to using the circumferentialsurface of the bristles for surface treatment purposes by structuring orprofiling it.

East German patent 32963 and U.S. Pat. No. 2,642,705 disclose theapplication of abrasive particles to the circumferential surface ofbristles or a bristle material by embedding the same in the surfacemelted-on bristle material. Such a procedure is not only verycomplicated, but it has also been found that the external abrasiveparticles can become loose in particular due to the bending actionoccurring when using the bristles. In addition, such bristles are soabrasive and therefore aggressive, that it is not possible to use themin all cases of human dental and body care.

It is known from U.S. Pat. No. 2,642,705, British patent 1 327 329 andin particular DE-OS 20 37 674 to incorporate by mixing abrasiveparticles into the plastics material of the bristles. According to DE-OS20 37 674 inorganic abrasive particles of aluminium oxide, chopped glassfibres, asbestos particles or ceramic material or also diamond particlesare used, which have a much greater hardness than the surroundingplastics material, so that there is a very pronounced abrading action,which in many cases is undesired. Frequently the abrasive particles areincorporated in such a high percentage that they touch or penetrate tothe bristle surface. Experience has also shown that such embeddedabrasive particles over a period of time are exposed as a result of wearon the surface of the bristle, so that the abrasiveness of the bristlesis significantly increased, so that such bristles cannot be used forhuman dental or body care, because it would lead to considerable risksof damage to the skin, teeth or mucous membranes of a user. In order toe.g. remove plaque from teeth or dirt from floors or roads, it is not somuch a question of obtaining an abrading action by abrasive material,but instead a so-called reaming action, which could be achieved by asurface structure or topography. Through the mixing in of abrasiveparticles such a surface structure can only be obtained when usingrelatively large particles. Admittedly the reaming characteristics ofsuch a bristle are adequate, but the large abrasive particles projectingover the surface simultaneously lead to high abrasiveness. The bristlesare also greatly weakened by the incorporation of large abrasiveparticles, so that the bristles only have an inadequate strength.

It is also known to mechanically roughen the surface of bristles, inthat the bristle flanks are structured with a tool (U.S. Pat. Nos.3,325,845 and 3,229,347). The roughening of the bristle flanks can bebrought about by means of an abrading or grinding device or also by sandblasting. However, this leads to the disadvantage that thelongitudinally oriented molecules in the bristles are torn open andconsequently the bristles are weakened. This procedure is also verycomplicated. After working the surfaces become fibrous and fringy, whichleads to the risk of parts being released from the bristle material. Ithas been found that it is not possible in this way to obtain a clearlydefined surface topography.

EP 360 938 A1 proposes embedding a blowing agent in the bristle materialand to bring about a surface roughness by foaming the blowing agent.However, the chambers or cavities forming throughout the bristle strandlead to a significant bristle stiffness reduction. In addition, due tothe torn open cavities the bristle surface is non-uniform and has noclearly defined structural depth or topography, which is necessary foreffective reaming.

SUMMARY OF THE INVENTION

The problem solved by the invention is to provide a bristle or bristlematerial, which has a predetermined surface topography with apredetermined or only slight abrasiveness, but an increased reamingaction. In addition, a method for the manufacture of the bristlematerial is to be provided with which corresponding bristles can beeasily manufactured.

With regards to the method, a thermally melted first plastics materialforming the main component of the extruded monofilament has a granularmaterial of a second plastics material with a higher thermal strengththan the first plastics material admixed with the latter before orduring extrusion. When using a thermoplastic material as the secondplastics material, the latter has a higher melting point. If,alternatively, another plastics material is used, it must be ensuredthat the latter does not liquefy or does not liquefy earlier than thefirst plastics material. The particle size of the granular material mustbe such that the monofilament during a subsequent drawing or stretchingis located in cross-sections in which there is little or no granularmaterial and is subject to a greater cross-sectional reduction ortransverse contraction than in cross-sections with a large amount ofgranular material. The granular material does not serve as abrasiveparticles, but merely as a shape or resistance body in order to locallyprevent transverse contraction.

In the method according to the invention the first plastics material,which can in known manner be polyamide, polyester, polyolefin, etc., isheated in an extruder and is consequently rendered flowable. Then,during or prior to extrusion the granular material from the secondplastics material is admixed in a quantity of preferably 5 to 30% of thetotal weight of the bristle material. The dimensions of the granularmaterial particles and their shape are dependent on the desired surfacestructure. The dimensions can fluctuate, but should not be too small. Ina preferred development of the invention, the size of the granularmaterial particles is between 10 and 50% of the diameter of the bristlematerial.

As the second plastics material of the granular material has a higherthermal strength or higher melting point than the first plasticsmaterial forming the main component, it can be achieved that as a resultof the heat of the first plastics material it does not or onlysurface-melts, so that the granular material particles during extrusionare contained as solid inclusions in the flowable, first plasticsmaterial.

According to the invention the granular material is also formed by aplastics material. This leads to the advantage that the granularmaterial can be produced in a simple manner, in that e.g. an extrudedmonofilament is produced and cut to length in the desired way. It hasproved advantageous to choose the length of the granular materialparticle either identical to or longer than the monofilament diameter.However, alternatively, it is also possible to produce the granularmaterial by grinding plastic. In order to obtain a relatively uniformparticle size, the granular material can be sorted in the conventionalmanner by a screening process.

It has proved advantageous to deburr the granular material. Particularlyin the case of granular materials produced by cutting to length amonofilament, relatively sharp edges occur, which could pass to theoutside in the case of bristle wear. These sharp edges are removed bythe deburring process, which can take place thermally and/ormechanically. In the case of thermal deburring, the granular materialundergoes surface premelting, so that the sharp edges flow. It isalternatively possible to surface-work in drums said granular materialprior to admixing with the first plastics material and consequently theedges are removed.

It has been found that for the granular material it is possible to alsouse higher thermally stable plastics which, as a result of theirmolecular structure, could not hitherto be used for bristle manufacture,because the technical values of the inventively manufactured bristlematerial are only dependent to a limited extent on the nature of thegranular material.

If the first plastics material with admixed granular material is forcedthrough the die of the extruder and the monofilament delivered is drawnoff at a speed which is higher than the delivery speed from the die, afirst stretching of the monofilament takes place. However, the tensileforces only act in the first plastics material, because the granularmaterial particles are contained in substantially freely mobile mannertherein. As a result of the stretching the coiled molecules of the firstplastics material are longitudinally oriented and the diameter of themonofilament is reduced by transverse contraction. The diameterreduction does not take place in uniform manner over the length, butinstead the granular material particles impeded transverse contraction,so that in the vicinity of a granular material particle there is a lowercross-sectional reduction than in areas where there are no granularmaterial particles. Therefore the stretching leads to a surfacestructure of the monofilament.

The still flowable monofilament with surface structure is subsequentlycooled in known manner, which leads to a solidification. Themonofilament is preferably subsequently exposed to a further stretching,which leads to an elongation to a much greater length and in particularto a further diameter reduction. The longitudinally oriented moleculesof the first plastics material are not destroyed. This can be followedin conventional manner by a stabilization of the monofilament or thebristle material.

If, according to a further development of the invention, theabrasiveness of the second plastics material of the granular material isat the most of the same level as that of the first plastics material, itis reliably prevented that the abrasiveness of the bristle material isdependent on whether and optionally to what extent granular materialparticles are located on the circumferential surface of the monofilamentor exert their action. Even if the bristle flank or circumferentialsurface is worn over a period of time and consequently the granularmaterial particles touch the circumferential surface, at the most thebristle has the same abrasiveness as the first plastics material formingthe main component.

According to a preferred development of the invention, the granularmaterial is embedded in the first plastics material and is substantiallycompletely covered by the latter. This is brought about in that thegranular material is so wetted by the first plastics material in theextruder, that on passing out through the die it is largely covered bythe plastics material. Therefore the monofilament has a circumferentialsurface, which is substantially completely formed by the first plasticsmaterial.

It has been found that the surface topography brought about by thezonally differing transverse contraction is dependent on the shape ofthe granular material particles and is in accordance therewith. Forobtaining different topographies, the granular material can bespherical, parallelepipedic or prismatic or can contain a mixture ofparticles with different shapes.

As has already been stated, the granular material need not melt duringthe extrusion process, so that the particles form a solid, dimensionallystable inclusion in the first plastics material. It is alternativelyalso possible for surface melting to take place during extrusion of thegranular material formed from plastic, so that it forms a solid bond andis surface welded to the surrounding first plastics material. However,it must be ensured that the granular material does not completely melt,because it would otherwise mix with the first plastics material.However, the surface melting can bring about a deburring.

For the first and second plastics materials, use is preferably made ofthermoplastic material combinations which can be readily weldedtogether. Particularly in the case of toothbrushes, it has provedappropriate to combine with the first plastics material of the bristles,Nylon 6.12, a polyphenylene sulphide granular material. The meltingpoint difference between Nylon 6.12 (218° C.) and polyphenylene sulphide(260° C.) has proved particularly advantageous.

Both the first and second plastics materials of the granular materialmay or may not be filled with fillers.

It has been found that the surface structuring is best visible ifrelatively little granular material is admixed with the first plasticsmaterial. However, this leads to a decrease in the abrasiveness due tothe small number of surface protuberances. In this case abrasiveness canbe increased again by adding fillers to the first plastics material.This makes it possible to obtain a slightly abrasively filled bristlewith a good surface structure.

It can be advantageous in certain applications for the granular materialto be harder than the first plastics material. In this case theformation of the surface structure is advantageously supported andmaintained in a lasting manner. However, alternatively, it is alsopossible for the granular material to be softer than the first plasticsmaterial. This leads to a more flexible surface structure, which isparticularly appropriate in means for the treatment of sensitive areas,e.g. the gums or interdental spaces. For this purpose it is possible forthe granular material to comprise a rubber-like material.

For certain applications it must be ensured that a user is able torecognize as such the reaming action-providing bristles according to theinvention and does not use the same by mistake. According to theinvention this can be achieved in that the first plastics material ismade transparent or translucent. Therefore the user can detect thecovered granular material, which preferably has a different colour tothe first plastics material, through the latter. For the visualizing ofany shape, size and action-differing granular material types, they canbe embedded in different colours in the transparent or translucent firstplastics material.

With regards to the bristle the aforementioned set problem is solved inthat the bristle is made from a first plastics material forming the maincomponent in which is embedded a granular material of a second plasticsmaterial in a substantially completely covered manner, the granularmaterial forming a structuring on the bristle surface. The abrasivenessof the second plastics material of the granular material can correspondat the most to that of the first plastics material. With such bristlesthe desired massaging and cleaning effects are not determined by thefiller or the granular material, but by the surface structures of thebristles resulting from the granular material dimensioning. Furtherfeatures and advantages of corresponding bristles can be gathered fromthe above description of the method. The aforementioned features andadvantages can also occur in a monofilament, such as is e.g. used incertain interdental cleaners.

The bristles or monofilament can have a random cross-sectional shape, inparticular round, oval, triangular, square, star-shaped, etc.

The invention also relates to a brush, particularly a toothbrush orinterdental cleaner, having a plurality of bristles optionally combinedinto bundles and in which at least some of the bristles are designedaccording to the invention. In order to adapt the action of a brush togiven framework conditions, the bristles according to the invention canalso be combined and processed together with bristles having otherconfigurations. Interdental cleaners are also known, which only comprisea single monofilament. The invention is also intended to cover thoseinterdental cleaners in which the monofilament is designed according tothe invention.

Apart from the aforementioned brushes, the invention can also be used inpaintbrushes for obtaining a better paint retention capacity, inhairbrushes for a good cleaning and degreasing capacity, in massagingbrushes with a better rubbing action, in manually and machine-operatedbrooms for increased dirt absorption, in polishing and abrading padswith a higher efficiency as a result of surface topography, as well asin woven, braided or other mats, cleaning equipment, applicators,polishing and abrading devices manufactured from bristles ormonofilaments. The invention can also be implemented in a filter which,due to its structuring, has an enlarged monofilament surface.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in greater detail hereinafter relative to anembodiment and the attached FIGS. 1 to 3, wherein show:

FIG. 1 A monofilament after extrusion in longitudinal section.

FIG. 2 The monofilament following prestretching.

FIG. 3 The monofilament after further stretching.

DETAILED DESCRIPTION

As can be seen in FIG. 1, immediately after passing out of the extruderdie, a monofilament 10 has a substantially uniform cross-section overits length with a smooth circumferential surface 13, several granularmaterial particles 12 of a second plastics material are embedded inirregular manner in a first plastics material 11 forming the maincomponent of the monofilament 10. In this embodiment the granularmaterial particles 12 in part have a spherical shape and in part aparallelepipedic shape. The first plastics material 11 is flowable,whereas the granular material particles 12 form solid, stableinclusions. After passing out of the extruder die (cf. arrows in FIG. 1)the monofilament is prestretched, so that it is subject to across-sectional reduction due to transverse contraction. However, thegranular material particles 12 zonally prevent this transversecontraction, so that cross-sections, where there is little or nogranular material particle or particles, are subject to a strongertransverse contraction than those cross-sections in which there arerelatively few granular material particles. This leads to a non-uniform,varying cross-sectional shape and size over the length of themonofilament, so that on the outside of the circumferential surface 13is formed a structuring, as can be seen in FIG. 2.

After cooling the monofilament is stretched again (cf. arrows in FIG. 2)and elongated to several times its previous length. This leads to afurther cross-sectional reduction due to transverse contraction, whichis once again prevented by the granular material particles. FIG. 3 showsthe resulting increased structuring of the circumferential surface 13 ofthe monofilament 10. It can be seen that the surface topography formedis dependent on the shape of the granular material particles. When usingspherical granular materials more gentle topography shapes are formedthan when using e.g. parallelepipedic granular materials.

What is claimed is:
 1. Method for the manufacture of surface-structuredbristle material from plastic comprising the steps of extruding amonofilament, in which with a thermally melted first thermoplasticmaterial forming the main component of the monofilament is admixed,before or during extrusion, a granular material of a secondthermoplastic material the abrasiveness of which is at most the same asthat of the first thermoplastic material, which has a higher thermalstrength than that of the first thermoplastic material, wherein thegranular material is surface-welded to the surrounding firstthermoplastic material during said extruding, and stretching themonofilament, wherein the particle size of the granular material is suchthat during said stretching, in cross-sections where there is little orno granular material, the monofilament is subject to a greatertransverse contraction than in cross-sections with a large amount ofgranular material to structure the outside of the circumferentialsurface of the monofilament with a non-uniform, varying cross-sectionalshape and size.
 2. Method according to claim 1, wherein after saidstretching, the monofilament is cooled, then further stretched andstabilized.
 3. Method according to claim 1, wherein the granularmaterial is admixed in a quantity of 5 to 30% of the total weight of thebristle material.
 4. Method according to claim 1, wherein the size ofthe granular material particles is between 10 to 50% of the diameter ofthe bristle material.
 5. Method according to claim 1, wherein thegranular material is embedded in the first thermoplastic material and issubstantially completely covered by the latter.
 6. Method according toclaim 1, wherein the granular material comprises spherical and/orprismatic particles.
 7. Method according to claim 1, wherein thegranular material is produced by cutting to length from an extrudedmono-filament.
 8. Method according to claim 1, wherein the granularmaterial is produced by grinding plastic.
 9. Method according to claim1, wherein the granular material is deburred.
 10. Method according toclaim 9, wherein deburring takes place thermally and/or mechanically.11. Method according to claim 1, wherein the second thermoplasticmaterial of the granular material is harder than the first thermoplasticmaterial.
 12. Method according to claim 1, wherein the secondthermoplastic material of the granular material is softer than the firstthermoplastic material.
 13. Method according to claim 1, wherein thefirst thermoplastic material is transparent or translucent.
 14. Methodaccording to claim 1, wherein the first thermoplastic material and/orthe second thermoplastic material is filled with fillers.
 15. Bristlewith a surface structure, said bristle comprising as a main component afirst thermoplastic material, and embedded in said first thermoplasticmaterial in a substantially completely covered manner a granularmaterial of a second thermoplastic material, the abrasiveness of whichis at most the same as that of the first thermoplastic material, saidgranular material being surface-welded to the surrounding firstthermoplastic material, the granular material forming a structuring onthe surface of the bristle such that the outside circumferential surfaceof the bristle is non-uniform, varying in cross-sectional shape andsize, and wherein the abrasiveness of said second thermoplastic materialof the granular material is at most the same as that of the firstthermoplastic material.
 16. Bristle according to claim 15, wherein thegranular material is admixed in a quantity of 5 to 30% of the totalweight of the bristle.
 17. Bristle according to claim 15, wherein thesize of the granular material is between 10 and 50% of the bristlediameter.
 18. Bristle according to claim 15, wherein the granularmaterial comprises spherical and/or prismatic particles.
 19. Bristleaccording to claim 15, wherein the second thermoplastic material of thegranular material is harder than the first thermoplastic material. 20.Bristle according to claim 15, wherein the second thermoplastic materialof the granular material is softer than the first thermoplasticmaterial.
 21. Bristle according to claim 15, wherein the firstthermoplastic material is transparent or translucent.
 22. Brush,particularly toothbrush or interdental cleaner, with a plurality ofbristles optionally combined into bundles, wherein at least some of saidbristles comprise as a main component a first thermoplastic material,and embedded in said first thermoplastic material in a substantiallycompletely covered manner a granular material of a second thermoplasticmaterial the abrasiveness of which is at most the same as that of thefirst thermoplastic material, said granular material beingsurface-welded to the surrounding first thermoplastic material, thegranular material forming a structuring on the surface of the bristlesuch that the outside circumferential surface of the bristle isnon-uniform, varying in cross-sectional shape and size.
 23. Interdentalcleaner comprising a single bristle, said bristle comprising as a maincomponent a first thermoplastic material, and embedded in said firstthermoplastic material in a substantially completely covered manner agranular material of a second thermoplastic material, said granularmaterial being surface-welded to the surrounding first thermoplasticmaterial, the granular material forming a structuring on the surface ofthe bristle such that the outside circumferential surface of the bristleis non-uniform, varying in cross-sectional shape and size, and whereinthe abrasiveness of said second thermoplastic material of the granularmaterial is at most the same as that of the first thermoplasticmaterial.